1. Field of the Invention
The present invention relates to a heat exchanger, and is suitably applied to a radiator which cools engine coolant of a vehicle engine.
2. Related Art
Conventionally, a radiator has plural tubes, a first header tank connected to one flow-path end of each tube and a second header tank connected to the other flow-path end of each tube. Coolant introduced into the first header tank is distributed into each tube and is heat-exchanged with air while flowing through each tube. After heat exchange, coolant is discharged from each tube and is collected into the second header tank.
Recently, while the number of devices disposed in an engine compartment of a vehicle has been increased, size reduction of each device such as a radiator has been demanded to enlarge a passenger compartment of the vehicle without increasing a vehicle body size. It is proposed to reduce a volume of the header tank to reduce a size of the radiator.
However, the header tank has an opening through which coolant flows into the header tank, and the opening is open in a direction perpendicular to a longitudinal direction of the header tank, for example. Therefore, when coolant flows into the header tank, coolant changes a flow direction by approximately 90 degrees at the opening. Further, a sectional area of the header tank is relatively small due to volume reduction of the header tank in comparison with an area of the opening, a sectional area of a coolant flow passage of the radiator is largely decreased in the header tank. As a result, coolant may largely lose pressure thereof in the header tank, and flow resistance of coolant in the header tank may be increased.